1. Technical Field
The present invention relates generally to a Voice over Internet Protocol (hereinafter, abbreviated to “VoIP”) system and, in particular, to a method for controlling bandwidth therein.
2. Related Art
The VoIP is a new communication service system in which people make voice calls through the Internet network rather than through the PSTN (Public Switch Telephone Network). Unlike the old system, the new call system over the Internet uses a packet-based network so that people can make voice calls at lower cost, not paying domestic/overseas phone line charge. In addition, using ITU-T (International Telecommunications Union-Telecommunications standardization sector), H.323, the VoIP can send not only audio information but also video information.
The VoIP service work includes the Internet as a back-bone, and gateways and personal computers are connected to the Internet. Each gateway is associated with the PSTN, which is connected to phone terminals and fax terminals. The terminals (i.e., phone terminals, fax terminals, and PCs) are endpoints, meaning that during 1:1 communication or meetings, one can communicate with another through audio (essential), video (optional), and data (optional). Every terminal is for bidirectional communication with gateways and with other terminals. Especially, the gateways are essential components, enabling real time bidirectional communication through the Internet using terminals connected to the Internet, that is, the packet based network, such as PCs, and PSDN, or using terminals connected to ISDN (Integrated Services Digital Network), such as phone terminals and fax terminals.
The VoIP network might or might not have a gatekeeper. The gatekeeper is located between the Internet and the gateways. Mainly, the gatekeeper converts aliases (phone numbers, names) to IP (Internet Protocol) addresses during calls between terminals. More specifically, the gatekeeper performs admission control, network bandwidth control, zone management, call detail record & storage, terminal alive check, alternate gatekeeper, logging and statistics.
Generally, when the VoIP service network has a gatekeeper, the gatekeeper performs the function of bandwidth control. The control is accomplished by calculating a rough bandwidth based on the number of Internet calls that are pending in the gateway. For example, suppose that the occupied bandwidth per call is 10 kbps (kilo bit per second), and 200 calls are pending. Then, the currently used bandwidth becomes 2 Mbps (mega bits per second). If T.38 fax call service is concerned, the gatekeeper, being unable to distinguish a fax call from a voice call, treats the pending call as a voice call and calculates the bandwidth usage anyway. What the fax call service really requires is about 20 kbps to 30 kbps occupied bandwidth per fax call. However, as the gatekeeper regards the fax call as another voice call and calculates the bandwidth usage therefrom, it is difficult to determine the actual total bandwidth usage.
In the case of a VoIP service network without a gatekeeper, the gateway or endpoint is not informed of the current trafficability of a remote gateway so that it cannot calculate the bandwidth usage in any way. For that reason, the VoIP service network without a gatekeeper could not perform effective VoIP call routing.